Organosulfur molecular weight modifiers or regulators in emulsion polymerization systems have exhibited somewhat variable efficiencies. Higher molecular weight species, particularly the mercaptan compounds, possess relatively low chain transfer effectiveness. Lower molecular weight species have higher volatilities which may contribute to residual odors in the polymeric product. Further, relatively high loss or depletion of the organosulfur molecular weight modifier has been observed in the first stages of monomer conversion, particularly about the first 10 percent conversion of monomer, in the emulsion polymerization process. Such high loss or depletion reduces effectiveness of the organosulfur molecular weight modifier, requiring use of increased amounts, thus increasing the cost of the polymer, as well as resulting in variations in product quality. It is certainly preferable for both economy and product quality with minimum residual odor to use minimum amounts of modifier consistent with effectiveness.